1. Field of Invention
The invention relates to a microfluid control device and the method. In particular, the invention relates to an air-driven microfluid control device and its method that use an external air source as the fluid power source.
2. Related Art
With the development in biotechnology, various biochips analyses utilizing proteins and DNA's are getting popular. The biochip takes very few specimens and test agents and has them undergo a series of fluid processing steps for the biochemical materials in the chip to fully mix with the test agents for reactions. Since the whole process happens on a tiny chip, how to control and transport fluid inside the chip becomes relatively important. Some microfluidic driving devices are thus invented, having the functions of controlling fluid transportation and preventing specimen and test agents from polluting each other. To satisfy the medical and biochemical testing requirements, disposable biochips with low costs and easy to control are important subjects under study.
At the current stage, the methods of driving fluid on chips can be divided into two types: the built-in-chip type and the external server driving type. The built-in-chip type includes mechanical micropumps and non-mechanical micropumps. The mechanical micropumps are comprised of pumps, actuators, and stop valves. Since the complicated microstructure of this type of mobile devices is manufactured using micro electro-mechanical system (MEMS) processes, the costs are relatively higher.
The non-mechanical micropump has different constraints for different designs. According to the driving methods, there are thermal-bubble, electrohydrodynamic, electro-osmosis, and electrophoretic micropumps. The thermal-bubble ones require appropriate tunnels designs. The electrohydrodynamic, electro-osmosis, and electrophoretic ones are limited in its driving range. The volume flow rate is smaller than 100 μl/min (10−6 L/min). One also has to impose a high voltage within a short distance. Generally speaking, the structure and control method of built-in-chip microfluid driving devices are complicated and expensive. They are thus unsuitable for disposable chips.
In comparison, the external server driving system moves the power for driving microfluid outside the chip, using a non-contact method to drive the fluid inside the chip. Therefore, the chip structure can be simplified and the cost also gets lower. The currently developed air-driven fluid driving system uses the on/off combination of five air valves to generate the pushing and pulling forces, thereby controlling the fluid inside the chip. For details, please refer to the U.S. Pat. No. 6,192,939. Nonetheless, the method involving the on/off combination of five air valves is too complicated. Such complications also increase the cost of the whole system.